Gaskets of the above-mentioned type, of which there are several known designs (see for instance Canadian Patent No. 971,997 dated July 29, 1975, and Canadian Patent No. 1,073,938 dated March 18, 1980, both to John Ditcher and entitled GASKET SEAL BETWEEN SEWER PIPE AND MANHOLE OPENING and MOLDED PLEATED GASKET respectively) have certain disadvantages, inter alia the following:
(a) they allow only very limited inclination of the sewer pipe with respect to its normal axis perpendicular to the plane of the manhole opening;
(b) they do not seal completely around the pipe when the latter is subjected to an abnormally high shearing stress;
(c) the pipe once inserted into the manhole opening often cannot be withdrawn for inserting its outer end into the bell-shaped spigot connection of the adjacent sewer pipe without breakage of the gasket;
(d) a poor seal often effected around the pipe due to surface irregularities of the pipe surface.